The appetite suppressant chlorphentermine is structurally similar to p-chloromethamphetamine, and it is an effective inhibitor of serotonin uptake. It has been reported that chlorphentermine does not deplete serotonin in whole rat brain, however, and the effect on trytophan hydroxylase has not been studied. We will examine the effect of chlorphentermine on tryptophan hydroxylase activity and serotonin levels in various regions of the rat brain to determine whether there is an effect which is masked in the whole brain.